Cuculus canorus is a brood parasite. The female cuckoo lays her egg in the nest of another species. The cuckoo egg closely resembles the egg of the host species' egg. The eggs of cuckoos are either spotted or solid in color, depending upon the color of the host species' egg. The egg mimicry is an adaptation to parasitism. When the host species leaves the nest unattended, the female cuckoo removes one of the host's eggs from the nest, then lays her own before the host returns. The cuckoo egg is incubated for about 12 ½ days and usually hatches before the host eggs. Once the cuckoo has hatched, it will eject the other eggs or young so that it will receive all the food brought by the "foster parents." The young cuckoo is fed and brooded by the host for 20- 23 days, and grows several times larger than the hosts. (Campbell and Lack 1985; Gooders 1982)